1. Field of the Invention
Magnetic broom, brush, or rake for sweeping an area clear of magnetically attractive debris, particularly for picking up nails and the like from a construction site.
2. Description of the Prior Art
Magnetic sweeping devices are known in the prior art and have been used in a variety of situations involving collection of ferro-materials. Certain activities in construction or repair of buildings scatter nails over the work site. Most notably, re-roofing of dwellings releases thousands of nails, many of which fall to the attic floor insulation and ground around the building. In most cases, these are grass lawns, driveways, flower beds, and other places where loose nails are considered a hazard. The present invention is specifically designed to retrieve nails, nail parts, and staples from just such difficult and varied surfaces as well as indoor surfaces such as a factory floor.
Most previous inventions for picking up magnetic debris from surfaces rely on fixed magnets, with or without pole pieces, supported a fixed distance over the surface. Most use bar or rod magnets oriented transversely to the preferred direction of motion.
MAGNETIC SWEEPER CONSTRUCTION, U.S. Pat. No. 5,285,904, Feb. 15, 1994, by Gerald A. Hasse, and his U.S. Pat. No. 4,407,038, Oct. 4, 1983, are typical of this genus. The support spacing is provided by wheels. The spacing away from the floor necessarily reduces the attracting field at the floor. The debris is collected in the space between the magnet and floor. Haase discloses that his magnets are spaced apart, but does not disclose the direction of magnetization or orientation of the poles. Haase's invention should operate most effectively with the magnet polarization N-S in the direction of the motion, i.e., transverse to the axle. Haase has spacing in other embodiments clearly to provide means to have lateral flexibility in his magnet assembly. In all embodiments, the spacing is the result of end walls on the magnet holding chambers. With the polarization suggested above, spacing has no affect on the effectiveness of the invention.
MAGNETIC RAKE, U.S. Pat. No. 5,395,148, by G. Jameson, et al, Mar. 7, 1995, is a variation of the spaced above the surface design, where bar or rod magnets are enclosed in a non-magnetic tube which is slid over the surface being cleaned. This puts the magnets very close to the floor, preserving the strength of the magnetic field. Debris is often trapped between the tube and floor, causing the likelihood of scratching the floor. When used in grass, Jameson's invention bends the grass stems over, trapping the nails under the grass, preventing the magnet from lifting them out of the grass mat, Jameson's second embodiment is a flat plate design which exaggerates the problems described for the tubular embodiment.
Many patents are on file where similar magnet systems are mounted on various pieces of housekeeping, yard, or farm equipment, especially household vacuum cleaners, including two others by Gerald Haase earlier than the citations above.
The wheel supported genus of magnetic sweeper rakes does not mechanically penetrate the surface being cleaned, and do not have sufficient magnetic reach to get into rough or grassy surfaces; thus, they are generally unsatisfactory for use in grass, loose dirt, and the like.
SHAG RUG FLUFFING AND OBJECT RETRIEVING DEVICE, U.S. Pat. No. 4,155,298, by Forrest Spence, May 29, 1979 and his earlier version, U.S. Pat. No. 4,087,879, have a series of combing tines on a rotating body. The primary purpose of the invention is to comb out tangles and fluff shag rugs. Small rod magnets are within the tines, thus reach into the rug, but the action of the primary utility, combing the rug, tends to clear the debris from the tines, putting it back onto the rug. Mr. Spence's later improvement is in part to overcome this by providing a means to transfer the debris from the tines to a storage magnet.
Spence's tines are of non-magnetic material, which spaces the enclosed magnets from the work surface and reduces the force of attraction for pickup and/or retention to remove the debris from the rug.
3. Objects of the Invention
The present invention is designed to overcome the objections and limitations of the prior art as the following objects, descriptions, and claims will illustrate.
It is an object of the present invention to generate a strong magnetic field to pick up ferrous debris along a swathe over an indistinct surface and having entanglements such as is found in grassy areas.
It is a further object of the invention to have the magnets in contact with, and rolling over, the surface being cleaned.
It is a further object of the invention to have the magnets loosely mounted on a bearing shaft so that transverse motion is permitted for working around small obstructions such as clumps of grass, clods of dirt, or rocks.
It is a further object of the invention to provide a handle so the magnetic rake invention is used in the manner of a push-broom.
It is a further object of the invention to provide a place for tying a hoisting rope to the invention for lifting onto a high place such as a building roof. The tying place may also be a gripping handle for easy manipulation of the tool.
It is a further object of the invention to focus the magnetic field to reach before, under, and behind the axis of the magnet assembly.
It is a further object of the invention to provide magnetic field that tends to direct debris away from the rolling surface to a storage zone.
The foregoing and other objects and advantages of this invention will appear from the following descriptions taken in connection with the accompanying drawings of the preferred embodiment.